The Drosophila melanogaster embryo DNA polymerase will be purified to homogeneity in the 9.0S enzyme form. The subunit structure of the high-molecular-weight DNA polymerase will be demonstrated by denaturing polyacrylamide gel electrophoresis. The purity of the enzyme will be examined by chromatographic and electrophoretic analyses. When the purity of the DNA polymerase is established, anti-DNA polymerase antibodies will be raised. The conversion of the 9.0S DNA polymerase to the 7.3S and 5.5S DNA polymerases will be studied using trypsin and other, specific proteases. The effects of structural conversion on the in vitro activity of the 9.0S enzyme will be investigated. Embryo extracts will be examined for their capacity to convert the DNA polymerase to various molecular forms and the specificity of enzymes that degrade to polymerase will be assessed. The dNTP and DNA binding subunits of the 9.0S and 5.5S forms of DNA polymerase will be demonstrated by affinity-labelling and biochemical techniques. The in vitro activity of the 9.0S and 5.5S forms of DNA polymerase will be assessed on natural templates of known sizes and structures, and conditions for in vitro activity will be optimized. Homopolymeric template-primers will be used to determine whether the polymerases utilize or remove mismatched primer termini. Stimulatory proteins will be isolated from cleavage-stage Drosophila embryos. The time and site of synthesis of the embryonic DNA polymerase during oogenesis will be determined using biochemical and immunological procedures. The activity of newly synthesized DNA polymerase will be determined in a micro-assay procedure to determine whether the polymerase is stored in oocytes in an inactive form.